Fig. 1

Refractive index reconstruction from 2D FDTD simulations. a False color image of the cell phantom with refractive index values of the medium (blue, 1.333), the cytoplasm (orange, 1.365), the nucleus (yellow, 1.360), and the nucleolus (red, 1.387). b As the cell phantom is rotated through the angle ϕ, from 0 to 360 degrees, the projections of a plane wave (sinogram) are computed with FDTD simulations. Displayed is the phase of the background-corrected and numerically refocused field that is used for the reconstruction. Red values indicate high phase retardation and blue values indicate low phase retardation. c, d, e Reconstruction of the cell phantom with the Born (c), Radon (d), and Rytov (e) approximations. f Line plots through the reconstructed cell phantom along the lines indicated in (c), (d), and (e). A total of 200 projections were used for the reconstruction